Brewing an Imperial Porter - Need Idea for Second Runnings

I will be brewing an imperial porter with a gravity of about 1.086 to 1.088 this weekend and looking for suggestions for a second running’s batch.

I haven’t done it before and could use some help, including, wort collection and storage if necessary. With one burner and kettle, it will have to wait until the next day if the brew day runs late.

What can I make from the second running’s, what kind of gravity can I expect, how much wort should I collect the second time around, and what amendments should I ad?

In the freezer I have plenty of DME and about a pound of Perle. I have some WLP530 stored from a Westy 12 clone too. Not sure how any of this would work but maybe a weird Belgiany porter with a pound of caramelized raisins, brown or Mexican sugar, or …?

The grist bill is …

Amt Name %
9 lbs 8.0 oz Pale Malt, Maris Otter (3.0 SRM) 51.0 %
2 lbs 4.0 oz Barley, Flaked (1.7 SRM) 12.1 %
2 lbs 4.0 oz Mild Malt (4.0 SRM) 12.1 %
1 lbs Caramel Malt - 120L (Briess) (120.0 SRM) 5.4 %
1 lbs Chocolate Malt (450.0 SRM) 5.4 %
12.0 oz Oats, Flaked (1.0 SRM) 4.0 %
12.0 oz Wheat, Flaked (1.6 SRM) 4.0 %
6.1 oz Caramel/Crystal Malt - 80L (80.0 SRM) 2.0 %
5.0 oz Caramel/Crystal Malt - 30L (30.0 SRM) 1.7 %
5.0 oz Kiln Coffee Malt (165.0 SRM) 1.7 %
2.1 oz Black (Patent) Malt (500.0 SRM) 0.7

You can probably get some 1.040 wort out of the second runnings, although if you’re short then a little DME will boost things. I’d probably just go for a British mild although a dubbel would work too.

An English dark mild would work well.

For the second beer, I downsized the original recipe to 2 gallons in Beersmith (sans hops and yeast), added the grains, about 4.5 pounds to the second mash, and collected about 4.5 gallons.

I added 1.5 oz. of fuggles at 60 minutes, 1 pound of grated piloncillo, 1 pound of caramelized raisins, and .5 oz. of fuggles at 15 minutes.

The raisins were hit with a propane torch to until the skin blistered and bubbled. I drew wort off the kettle, pureed the raisins, and dumped the slurry into the hop bag to keep the wort clean.

With a lid on the keggle, I boiled the first addition of hops and raisins for 30 minutes.

Post boil, the gravity at 3.75 gallons was about 1.068-1.070. I pitched an active slurry of WLP530 and let it go.

I decided not to add O2 for this batch, just to see how it goes. The fermentation chamber is occupied with the first batch so this one is sitting in the garage at an ambient temp of 64F. Measuring the beer internally, it is 70F.

Hope it tastes good.